The frequency of transmission of HAA, anti-HAA and hepatitis from mother to infant will be studied by the prospective HAA monitoring for 6 months of all infants of women with maternal and post-partum hepatitis and those found to be HAA carriers at the time of delivery. The time interval between maternal hepatitis and infant HAA antigenemia and/or hepatitis may suggest the mode of transmission. Transplacental transmission will be studied by HAA testing women with hepatitis during pregnancy and at birth; testing the cord blood, amniotic fluid and neonate at delivery; and HAA monitoring the infant for 6 months. Post- partum transmission will be studied by HAA monitoring of mother and child for at least 6 months when the mother develops hepatitis from blood transfusion for post-partum hemmorrhage. Breast milk and vaginal blood of HAA positive women will be tested provisionally to colostral and vaginal transmission. The incidence and time of onset of hepatitis- associated antigenemia and/or hepatitis of infants at risk will be determined by monthly clinical, HAA and SGPT examinations for at least 6 months. The natural course of HAA positive hepatitis, when it occurs, will be recorded with careful clinical observation and appropriate laboratory testing for the duration of the illness. The documentation of HAA persistence in infected infants will require periodic HAA testing for prolonged (years) and probably indefinite periods of time. Similarly, the question of the incidence and type of post-hepatitis sequelae such as persistent hepatitis, chronic active viral hepatitis, cirrhosis and hepatoma will be ascertained by clinical laboratory follow-up for an indeterminate period of time coupled with a detailed study of those patients in whom such illness(es) evolve.